I was using Parallels on Mac OS X, but I just switched over to Virtualbox. Parallels is horribly slow compared to both Virtualbox and VMWare, or at least it seems so. The first version they released under Sun's leadership is 1.6.2, and it seems to have quite a bit more features and support for operating systems.

I really am enjoying my using VirtualBox. While it is the lesser known product it has two things going for it in my workplace. 1) The ability to run Solaris as a host. 2) The open source version will compile and run with a FreeBSD host. I notice you did not list Virtual PC.

Question: Am I missing something about Xen or did virtualbox end up incorporating xen once Sun owned them all?

You really need to specify which type of virtualisation software you want to discuss. I was all set to vote and post some long comments ... but then realised you were only discussing host-based VM software (VMWare Server/Player/Workstation, QEmu, VirtualPC, etc). That's so blase.

Now, if you want to talk about hypervisors (Xen, Linux-KVM, VMWare ESX) and other lower-level VM software (and hardware), I'll be all over that.

VirtualBox only uses Qemu code for certain things. Otherwise, much of the code is still different from whatever else is available.

Here's what I'm really wondering about, at least ever since I read that VMWare's model is to run as many instructions natively as possible. What's the role of CPU VT instructions, then? I thought that CPU VT instructions made this possible, but VMWare has been doing this before the instructions were ever available.

By the way, KVM was listed. I said "Qemu (various combos or not)". Xen is in a class all on its own, which is why it's not appropriate here. I don't think Virtual PC is available for Unix...

Here's what I'm really wondering about, at least ever since I read that VMWare's model is to run as many instructions natively as possible. What's the role of CPU VT instructions, then? I thought that CPU VT instructions made this possible, but VMWare has been doing this before the instructions were ever available.

VMWare Player/Server/Workstation do everything in software. The CPU virtualisation features aren't used. They do binary translation and patching of instructions in memory.

Latest versions of VMWare ESX/GSX, I believe, can make use of the virtualisation features in CPUs. But I have very little info on that subject.

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By the way, KVM was listed. I said "Qemu (various combos or not)".

That's like having a poll with MS-DOS (various combos) and wondering why nobody using Windows ME participated in the poll.

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Xen is in a class all on its own, which is why it's not appropriate here.

Except that VMWare ESX, KVM, and MS Hyper-V are all in the same class as Xen (hypervisor-based virtualisation).

There's nothing in the online library, the VMWare website, or the documentation that I could find on their site, that makes any mention of hardware virtualisation support in VMWare Workstation 6.0, VMWare Player 2.0, or VMWare Server 1.0.

According to their VMI Performance PDF, they continue to use binary translation, as their current implementation is faster than their experimental hardware virtualisation implementation. This is for VMWare Server ESX 2.0.

There is mention of a hardware assisted version of the VMM in this paper from 2006 that mentions experimental support for hardware virtualisation in VMWare Server 1.0.1. However, there is no mention anywhere (that I can find) on their website that says this is actually available and usable.

So, if they support hardware virtualisation, they go to great lengths to hide that information from the public.

Well, I couldn't find much information either, at least on official page presenting VMware Workstation. So I Googled a bit and found the reference link mentioning it. After Googling more I found these:

Now what Parallels probably means is that their virtual machine monitor takes advantage of hardware assist (Intel VT and AMD-V) on newer processors. VMware Workstation also takes advantage of Intel VT for 64-bit guests, but for 32-bit guests and AMD CPUs, we have a tuned binary translation (BT) monitor. In fact we've shown that for normal workloads, our BT monitor is as fast or faster than VT, and therefore we're more interested in the next generation of these technologies.

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